Even though according to the Oxford Italian English Dictionary: ogni scusa è buona per litigare any pretext will do to start a quarrel di ogni sorta of any kind in ogni momento at any time per loro ogni pretesto è buono they'll jump at any excuse a ogni modo at any rate a ogni costo at any cost, at all costs
Duolingo counted "they used any argument possible" incorrect!
Hmm. To me as an Aus Eng. speaker, "any argument" implies many of the arguments were bogus, fabricated, irrelevant etc and they were desperate to win this debate by any means. Whereas "every argument" implies all the arguments were valid, and they used them all to win the day, by just weight of reason. So, I tend to favour the "every argument" translation. But this is just my guess at what the context of the Italian phrase might be.
The adverb modifies a verb, adjective or another adverb and not a noun. Therefore, this English sentence is not properly translated. It should be translated as THEY USED EVERY POSSIBLE ARGUMENT where possible is an adjective modified by the adverb every and possible is the adjective modifying the noun argument. MR DUO PLEASE REVISE THIS SENTENCE which is confusing people like me learning English.